Guided wave radar level transmitters are used to measure fluid levels in closed tanks, open tanks, reservoirs, and other environments. A guided wave radar level transmitter sends a short Radio frequency (“RF”) pulse along a probe that penetrates into the tank containing the product to be measured. The RF pulse is reflected off of the product surface back to the GWR electronics. The time of flight of the pulse is used to calculate the position of the product surface, and thus the product level can be determined. The coaxial type of GWR probe is comprised of an inner rod conductor and a coaxial tube. The RF electronics can be attached with the signal passing into the sensor's inner conductor while the outer conductor is connected to ground. The RF pulse's field is contained within the outer conductor making coaxial probes insensitive to surrounding obstructions that would interfere with other probe types (such as wire or rod probes).
The coaxial probes have an inner rod, an outer tube, and a spacer that centers the rod within the shell. The spacers cannot be solid because solid spacers prevent the fluid from flowing up the inside of the probe between the inner rod and the outer tube. The spacers should also be restricted from moving up and down the inner rod. Some retention strategies use discontinuities, such as shoulders, detents, or indentations to restrict spacer movement. These discontinuities can cause measurement errors. Systems and methods for improved spacer retention are needed.